1. Field of the Invention
This invention relates generally to voice and data communication systems, and more particularly to wireless transmission protocols.
2. Description of the Related Art
Bluetooth is a short-range radio standard intended to replace the cables connecting portable and fixed electronic devices. The standard, which operates in the unlicensed Industrial-Scientific-Medical (“ISM”) band at 2.4 GHz, focuses on robustness, low complexity, low power, and low cost. A frequency-agile or frequency “hop” protocol is applied to provide security and limit interference, and a shaped, binary FM modulation is used to minimize transceiver complexity. A symbol rate of 1 Ms/s, is maintained with a slotted channel having a nominal slot length of 0.625 msec.
For full duplex transmission, a Time-Division Duplex (“TDD”) scheme is implemented. Under a TDD scheme the same channel is broken into time slots, with specified time slots used for transmitting and others for receiving. Information is exchanged through data packets which typically cover a single slot, but which may be extended to cover up to five slots, depending on the application. Additional features of the Bluetooth standard are described in Jaap Haartsen, Bluetooth—The Universal Radio Interface for ad hoc, Wireless Connectivity, ERICSSON REVIEW No. 3, (1998).
Referring to FIG. 1, the “Bluetooth” specification is comprised of several different protocol layers including a radio frequency (“RF”) layer 160, a baseband layer (“BB”) 150, a link control layer (“LC”) 140, a link manager layer (“LM”) 130, a logical link control and adaptation protocol layer (“L2CAP”), and a serial line emulation layer (“RFCOM”). The functionality of each of these layers (as well as additional Bluetooth protocol layers) is described in detail in Bluetooth Protocol Architecture, Version 1.0 (Aug. 25, 1999) (“Bluetooth Protocol Architecture”), which can be found at “http://www.bluetooth.com.”
Because Bluetooth is defined as a bidirectional protocol, devices are typically required to have both a receiver and a transmitter in order to comply with the Bluetooth standard (i.e., the Bluetooth protocol assumes bi-directional signaling for all devices in a Bluetooth network, referred to as a “piconet”). However, a number of potential Bluetooth devices (e.g., keyboards, mice, microphones, speakers, ear pieces, . . . , etc) are not bidirectional in nature. The applications these devices support exist only as data sources or as data sinks. For example, wireless input devices such as a wireless keyboards are typically only required to transmit data. Similarly, wireless output devices such as wireless audio ear pieces or wireless video monitors are typically only required to receive data. Accordingly, from an application standpoint, these devices only require unidirectional communication.
What is needed is a system and method for providing unidirectional communication between wireless devices when bidirectional communication is unnecessary. What is also needed is a system and method for synchronizing data transmission between wireless devices when unidirectional communication is implemented. What is also needed is a system and method which will work seamlessly with the Bluetooth protocol.